The instant invention relates to a process and device for reducing energy consumption in the operation of spinning rotors of an open-end spinning machine or in the operation of the spindles of ring spinning machines or of the roving frame.
The spinning elements are considered, for example, to be spinning rotors and spindles. The drive of the spinning elements is designed so that indirect driving means (belts or drive disks) are pressed interlockingly against the driving surface assigned to the spinning element. This drive can also be designed so that a motor drives a group of spinning elements by means of a belt drive, or so that an indirect motorized individual drive is provided for each spinning element, whereby belts or driving disks are acting as indirect driving means.
It is known that a consumption of energy is expended as a result of the slip between spinning elements and their indirect driving means, and that this slip is not negligible from the point of view of energy consumption even when optimal production conditions are ensured. The admissible deviation in rotational speed for the nominal operation of the rotors lies within a tolerance range of approximately .+-.2% without affecting the product quality. The deviations of rotational speeds of the rotors from each other lie within a tolerance range of .+-.1.5%. From this, it appears clearly that due to the tolerance of the rotational speeds of rotors from each other the electric consumption is not minimal, especially when rotors are driven by group drives by means of belts and a drive motor. This situation increases the overall consumption of energy by the spinning machine since the duration of normal operation is very long as compared with run-up and stoppage.
DE-OS 39 42 402 describes a tangential belt drive of an open-end spinning machine in which the spinning rotors of several adjoining spinning units are driven. The described actuating mechanism is directed only upon the alternation between rotor, brake and pressure roller. This makes it possible to increase the contact pressure by an always constant value during the run-up of the spinning machine and to reduce it again as normal operation starts. This process is conditioned upon the action of a service carriage upon the common actuating mechanism of brake and pressure roller. The run-up phase takes place in a matter of seconds, so that the energy savings which can be obtained are minimal. Since the intervention of the automatic service carriage is necessary, the effect of energy savings applies in each instance only to one single rotor of the spinning machine, whereas the machine has, as a general rule, over 200 rotors. The actual economic result with respect to energy savings for the entire machine is very low. The total time for all piecing processes in a spinning machine per shift is considerably lower than the total time of yarn production per shift. It is therefore a disadvantage that no energy saving can be achieved with this solution for the entire time of yarn production of the spinning machine. For this critical period of time, the solution is absolutely unsuitable in achieving any kind of energy saving.
DE-OS 34 13 764 describes a device having similar disadvantages. The knowledge of these two solution is obviously insufficient to achieve energy savings with economic impact for the entire operating time of the machine per shift.
As stated in the article "Autocoro 240 for the production of fine rotor yarns", Chemiefasern/Textilindustrie, 41./93, January 1991, page 41, efforts to reduce energy consumption in a spinning machine have tended towards the utilization of rotors with smaller rotor diameters for instance, the control of drives with frequency reversers or the utilization of new twin disk bearings for the rotors. In the described solutions no possibilities are shown on how the conventional pressure roller may be used to contribute to a reduction of electrical consumption to a minimum during the entire time of production.
The solution according to DE-AS 15 10 840 achieved an improvement over the rigid pressure which is independent of rotational speed. It is, however, a disadvantage of this solution that the force of contact pressure is changed only centrally, i.e. simultaneously and uniformly at all pressure rollers. The existing tolerance (.+-.1.5%) for the rotational speed difference between spinning elements for example, cannot be taken into consideration in any satisfactory manner for the reduction of energy consumption. It is furthermore disadvantageous for the contact pressure to be controlled only centrally, i.e. the reactions to adjustments cannot be recognized, and this results in energy loss for the individual spinning element because of the tolerance. Until now the existing tolerance has prevented any further lowering of energy consumption during spinning operation.
It is a known fact that due to the slippage between spinning elements and their indirect driving means energy consumption which is not minimal, even when optimal production conditions are ensured, continues to exist.
It would be possible to achieve considerable savings in three-shift operation of a spinning machine in the order of up to one fourth of present energy consumption for the rotor drive, if energy losses due to uncontrolled slip between rotor and indirect driving means can be avoided. The existing situation is especially aggravating because the time for normal operation is very long by comparison with operating states such as run-up or stoppage, and therefore exerts the decisive influence upon the potential energy savings.